The sensitivity of widely used silver halide photographic materials has increased over the years from an ISO sensitivity of 100 to an ISO sensitivity of greater than 1000. Emulsions containing large silver halide grains, which give greater sensitivity to light, may be used to increase speed; however, such emulsions may also increase granularity. In addition, certain silver halide emulsions are relatively more difficult to develop depending upon their particular physical or chemical properties. For example, silver halide emulsions with large grains or silver halide grains having relatively high iodide content, generally develop at slower rates than emulsions having smaller grains or low iodide content.
Therefore, it is desirable to invent a technique that achieves higher speed with smaller silver halide grains. Methods to accelerate development of exposed silver halide grains have been realized. For example, U.S. Pat. No. 4,912,025 describes the release of electron transfer agents (ETA)s for development acceleration without a concomitant granularity and fog increase. These types of compounds are commonly referred to as electron transfer agent releasing couplers or (ETARC)s. As another example, U.S. Pat. No. 5,605,786 describes a method of imagewise release of an ETA where an --O--CO--(T).sub.n --(ETA) group is attached at the coupling-off site of the ETARC.
The inventors herein have found that the disadvantage of previous ETARC compounds is that the released ETA fragment migrates out of the layer it in which it is coated. This undesired movement of the ETA creates unwanted dye density in the adjacent layer as a function of development of the primary layer and is commonly referred to as wrong way interimage. Wrong way interimage can be greatly decreased if the acceleration effect of the ETA is localized in the layer in which the ETARC is placed. Thus, there is a need for the development of methods for localizing this acceleration effect.